Nonlinear optical materials and processes employing diacetylenes

ABSTRACT

Novel nonlinear optical, piezoelectric, pyroelectric, waveguide, and other materials are presented together with processes for their employment and articles formed thereby. Such materials, processes and articles comprise diacetylenes and polymers formed from diacetylenic species, which polymers are amenable to close geometric, steric, structural, and electronic control. Accordingly, it is now possible to design, formulate and employ new diacetylenic species and polymers formed therefrom to provide nonlinear optic, waveguide, piezoelectric, and pyroelectric materials and devices having surprising efficiencies and degrees of effect. 
     According to a preferred embodiment of the invention, diacetylenes which are crystallizable into crystals having a non-centrosymmetric unit cell may form single crystals or may be elaborated into a thin film upon a substrate by the Langmuir-Blodgett technique. Such films may, optionally, be polymerized either thermally or by irradiation for use in nonlinear optical and other systems. According to other preferred embodiments, diacetylenes are covalently bonded to substrates through the employment of silane species and subsequently polymerized to yield nonlinear optic and other devices having high structural integrity in addition to high efficiencies and effects.

This work has been supported by funds from the Defense Advance ResearchProjects Agency, project designation DAAK 70-77C-0045.

RELATED APPLICATIONS

This is a division of application Ser. No. 129,560, filed Mar. 12, 1980,now U.S. Pat. No. 4,431,263 which is a continuation-in-part of Ser. No.052,007 now abandoned filed June 25, 1979. This is also related tocopending Application Ser. No. 113,552 filed Jan. 21, 1980 and nowabandoned which is incorporated herein by reference.

INTRODUCTION

This invention is concerned with novel materials useful in theelaboration of thin film, single crystal and other devices; processesuseful for such production, and articles formed thereby. Moreparticularly, the invention is drawn to nonlinear optical and othermaterials suitable for use in electro-optical, second harmonicgenerating, electro-acoustic, piezoelectric, pyroelectric, waveguide,semiconductor and other devices especially those wherein arrays oraggregates of films or layers may be employed as constituents.

Thin film, single crystal and other devices such as those describedabove are known to those skilled in the art, as are the basic principlesunderlying their design, fabrication, and use. This invention isdirected towards materials, especially nonlinear optical materials,which are tailored to the physical, electronic, and chemicalrequirements of the various devices, toward novel means for theefficient employment of such materials and toward articles whichincorporate the same. Thus the requirements of symmetry, electronicconfiguration, physical organization, chemical bonding, and overallsuitability are met by a systematic approach to design and fabricationemploying a class of materials uniquely suited for maximization of thesefactors and effects.

The superiority of the present invention over the materials, processesand articles known to the prior art will be readily apparent. Thus foruse in electro-optic, second harmonic generating and other nonlinearoptical systems, the materials of this invention evidence figures ofmerit more than one thousand times better than the commonly usedinorganic perovskites such as lithium niobate. Furthermore, certain ofthe materials preferred for use in accordance with the present inventionare not only capable of optical second harmonic generation, butgeneration which is phase matchable. This property will be recognized asbeing highly desirable in such systems. In the piezo- and pyroelectricfield, the diacetylenic species taught hereby represent a ten foldincrease over lithium niobate. At the same time, the present systems mayserve as waveguiding media which exhibit loss rates as low as from 0.01to 0.1 db/km, while at the same time exhibiting unparalleled ease offabrication. Thus, the present invention presents a single systemcapable of these various uses. It will be readily apparent to thoseskilled in art that optical switching, processing and logic devices ofunparalleled performance may be fabricated employing diacetylenesaccording to this invention.

The compositions, processes and articles of this invention employmembers of the chemical genus of diacetylenes which are molecules havingat least two acetylenic bonds in conjugation with one another. It hasbeen found by the inventor that members of this genus are uniquelysuited for such employment as they possess the chemical and physicalproperties which may be tailored to the particular requirements of thedesired systems. See in this regard the pioneering work by the inventor"Origin of the Nonlinear Second-Order Optical Susceptibilities ofOrganic Systems", A. F. Garito et al., Physical Review A, vol. 20 No. 3pp 1179-1194 (September 1979), which article is incorporated herein byreference.

More particularly, it has been found that a class of diacetylenes may beformulated which are non-centrosymmetric species, that is, which have nocenter of symmetry on either the molecular or crystalline unit celllevel. These non-centrosymmetric species, especially those which haveone or more chiral centers, fluid particular utility in certainembodiments of the present invention.

The term "electro-optic effect" refers to a change in the refractiveindex of a transparent substance induced by an applied electric field.Devices based on this effect have been used since the turn of thecentury for the control of light; only recently, however, has the adventof the laser stimulated great interest in the study and application ofthe effect and its materials implications. By various manipulations ofthe electric field acting upon electro-optic media, a manipulation ofthe transmitted light may be obtained. Thus, modulation, polarization,frequency selection, amplification, frequency modification, and otherresults may be observed. An Introduction to Electro-Optic Devices byIvan Kaminow, (Academic Press, 1974) provides a good introduction to thefield and defines some common and exemplary electro-optic and othersystems both explicitly and by reference.

The phenomenon known as second harmonic generation or SHG may be seen tobe a special but distinct ase of the electro-optic effect. Certainmaterials are suited to the production of optical harmonics upon thetransmission of light therethrough. The predominant harmonic which isgenerated in such a case is the second harmonic, thus leading to theterm "second harmonic generation". This effect is described by Frankenand Ward in "Optical Harmonics and Non-Linear Phenomena" Reviews ofModern Physics, 35(1) pp. 28-39 (1963).

As will be recognized by those skilled in the art, the transmission oflaser light through a SHG medium will give rise to two light waves, eachhaving frequencies which are second harmonics to the incident beam. Itis difficult to utilize such second harmonic beams in most cases becausethe two beams may not be synchronous; they may be out of phase. In suchcases, interference or "beating" is evidenced and results in outputlight of diminished amplitude and utility. To overcome this effect, itis highly desired to employ SHG media which are "phase matchable". Suchmedia may generate two second harmonic waves which are synchronous,which do not show out-of-phase "beating" or interference. Such phasematchability is rare in SHG systems and is much to be preferred. Withsuch materials, the amplitude of a resulting phase matched secondharmonic is a maximum, is constant with time, and represents the highestattainable SHG efficiency for the system. Second harmonic generatingsystems may be devised which "cascade" light in two or more steps sothat the light frequency may be doubled, then redoubled, etc. Phasematchability is important in such systems to avoid excessive power loss.Second harmonic generating materials, especially those which are phasematchable, are highly useful in signal processing, laser detection, andother devices and fields of use.

An additional phenomenon which is related to the electro-optic effect isthe electro-acoustic effect. This phenomenon employs an acoustic signalto modulate an electric field experienced by an electro-optic device.Said signal, may, thus, be replicated in the transmitted light whichbecomes a suitable means for transmission of the signal. Those skilledin the art will recognize that other effects are known to be similar orrelated to the electro-optic effect and that such effects which arecollectively know as nonlinear optical effects, and devices employingthem are believed to be attainable through employment of one or more ofthe materials or processes of this invention; no limitation istherefore, to be implied from this necessarily limited discussion.

It is only recently that the nonlinear optic effects such aselectro-optic and related effects have come to be understood in anonempirical fashion. The inventor of this invention was the first tounderstand the physical and theoretical principles which underlynonlinear behavior in organic systems. In this regard, reference is madeto "Origin of the Nonlinear Second-Order Optical Susceptabilities ofOrganic Systems" by Garito, et al, Physical Review A, vol. 20, No. 3,PP.1179-1194, September 1979, which has been incorporated herein byreference. This understanding has enabled the design of materials andprocesses which are ideally suited to the requirements of electro-opticand related nonlinear optical systems.

Additional applications for the materials and processes of thisinvention which do not primarily rely upon nonlinearity are found in theareas of piezo- and pyroelectricity. Piezoelectricity, is a phenomenonwhereby kinetic energy and electrical potential may be intercoupledthrough the intermediation of a suitable piezoelectric medium. Thepyroelectric effect is manifested by a transformation between thermaland electrical energies through a pyroelectric medium. In practice, apiezoelectric device translates a physical stress into a current, or acurrent into a physical movement. It will be understood that ordinaryphonographic "pickups" are common embodiments of the former phenomenonwhile certain audio speakers exemplify the latter. Pyroelectric devicesare useful in, inter alia, temperature sensing, power generation andrelated applications. Both embodiments may benefit from use of thepresent invention; both will profit by the advantages and efficienciesavailable therewith.

The invention may also be employed in the formulation and fabrication ofoptical waveguides. Such guides are capable of perpetuating a standinglight wave through the guide, and of allowing said wave to be directed,manipulated and bent. While many waveguiding systems are known, thematerials of the present invention have a very high suitability forinclusion in such systems. Specifically, the evidence an excellently lowloss rate of from about 0.1 to 0.01 db/km, a figure which comparesfavorably with commonly employed organic species and which easilyoutshines perovskite type compositions which are known to exhibit lossesof from 5-10 db/km.

It will be understood that the foregoing is not intended to be arigorous definition of the electronic, optic, electro-optic and otherfields wherein the present invention may be employed, but, rather isintended as merely an illustrative explanation of certain of thosefields. Those skilled in the art will readily appreciate the wideapplicability of the materials and processes taught hereby and willunderstand that any electronic, optical, electro-optic, SHG,electro-acoustic, piezoelectric, pyroelectric, waveguide, semiconductorand other system which may benefit from close control of symmetry,steric, electronic, and physical elements of the constituent componentswill benefit through employment of this invention and that all suchsystems are envisioned hereby.

As will be discussed more fully below, nonlinear optic, piezo-, andpyroelectric systems are well known to require certain types ofasymmetry on the molecular and crystalline unit cell level. In addition,however, it has now been discovered that electro-optic, second harmonicgenerating and other nonlinear optic materials required additionalproperties for optimization of nonlinear effects. See in this regard thePhysical Review A article which has been incorporated herein byreference. Thus it has been found that a delocalized pi electronicsystem together with a suitable electronic ground and excited statemanifold structure are required for good performance in organicnonlinear optic systems. It is believed that the presence of adelocalized pi electronic system makes electronic excitations moreaccessible for interaction with electromagnetic energy; this isreflected in the susceptibility terms of the nonlinear opticalcalculations presented in the Physical Review paper. Thus a delocalizedpi electron system is believed to be vital to the efficient coupling oflight with the nonlinear optical materials. The requirement for asuitable electronic manifold is related to the desirability of having alarge difference in the ground state and excited state dipoles ofnonlinear optical materials. This large difference is reflected in alarge transition moment associated with electronic excitation and aconcomitantly large nonlinear effect being associated with thattransition. The diacetylenic system has now been shown to possess anideal delocalized pi electronic system for nonlinear optical use.Furthermore, the system has an appropriate electronic manifold and isamenable to substitution with species which improve the manifoldconfiguration still further.

The asymmetries demonstrated by certain classes of diacetylenes lend themolecules to employment in piezoelectric and pyroelectric devices aswell. Additionally, diacetylenes may be extremely useful constituientsof optical wave guides. This application, which does not necessarilyrequire asymmetric discetylenes, may be employed inter alia tointerconnect pluralities of nonlinear optical devices or the like toresult in integrated optical switching circuit arrays and similararticles.

It is, therefore, an object of this invention to provide novel materialsemploying diacetylenes for inclusion in thin film or single crystalnonlinear optical and other devices. A further object is to provideprocesses suitable for the elaboration and construction of such devicesand for other uses. A still further object is to furnish thin film,single crystal and other devices which are suitable for use aselectro-optic, second harmonic generating, electro-acoustic, othernonlinear optic, piezoelectric, pyroelectric, wave guide, semiconductorand other devices. Another object is to provide nonlinear opticalsystems which possess excellent pi electron and electronic manifoldsystems. Other objects are attained by the development of diacetylenicmaterials and processes whereby high efficiency, productivity andeffects may be achieved in device fabrication and whereby a systemsapproach to such fabrication may be had.

As has been indicated, materials suitable for use in nonlinear opticalsystems must meet certain requirements of symmetry and electronicstructure. Similarly, piezo-, and pyroelectric materials must satisfycertain symmetry conditions, while compositions suitable for waveguidingand other uses have no particular symmetry or electronic requirements.The materials of this invention offer the practitioner in the art agreat deal of flexibility in design and fabrication of these variousdevices by virtue of the ability to control closely the electronic andsymmetry components of the system.

The symmetry requirements for nonlinear optical materials have beenrecognized empirically. See Physical Properties of Crystals, by J. F.Nye (Oxford U.P. p. 2957, 1976); A. Yariv, Quantum Electronics (Wiley,1967); Molecular Crystals and Molecules, A. I. Kitaigorodsky (Academic,1973); and the Kaminow work cited previously. Thus it is known thatnonlinear optical materials such as electro-optic, SHG,electro-acoustic, etc. must exhibit non-centrosymmetry. This requirementis shared by piezo-, and pyroelectric materials and, indeed, it isrecognized that nonlinear optical materials are, of necessity,piezoelectric and pyroelectric as well. In this context,non-centrosymmetry refers to a state of having no center of inversionsymmetry on both the molecular and unit cell basis. Thus, suitablenon-centrosymmetric species not only are molecules which are asymmetric,but also are molecules which, when coalesced into a crystalline matrix,are also not symmetric vis-a-vis the unit cell of the crystal.

It is believed that the asymmetry of the unit cells is manifested byfinite electronic dipoles in the materials. Such dipoles are believed tobe necessary for interaction with an applied electric field; withoutsuch dipoles, coupling of the materials with an applied electric fieldis thought to be impossible.

It will be appreciated that molecules which are asymmetric on themolecular scale will tend to form symmetric crystalline unit cells; evenmany chiral molecules are known to so crystallize. It is, therefore,necessary to inquire as to symmetry on the crystal unit cell level todetermine the presence or absence of non-centrosymmetry and, hence, thesuitability of materials for nonlinear optical, piezo-, and pyroelectricuse.

While molecules having one or more chiral centers are, necessarily,non-centrosymmetric on the molecular level and, hence, are fruitfulcandidates for overall non-centrosymmetry as well, species which are notchiral may also form non-centrosymmetric cells. All such materials arecontemplated for use in this invention.

While symmetry considerations, thus, play a major role in selection ofnonlinear optical, piezoelectric and pyroelectric materials, waveguidingand other uses for the materials, processes and articles of thisinvention may employ symmetric species.

As has been suggested above, the electronic structure of the materialsused in the design and construction of the thin film, single crystal andother devices is of great importance to the performance of thesedevices. It has been discovered by this inventor that the natures of theground state and excited state electronic manifolds of a material havelarge impacts on the properties possessed by said materials in optical,electronic, electro-optical and other devices. Thus it has been foundthat for high electro-optic, SHG, electro-acoustic, and other nonlinearoptical effects a material must possess not only the requisite asymmetrybut also a suitable delocalized pi electronic system. Furthermore, theground and excited states must have a large charge separation asevidenced by large dipole moments and transition moments. The materialsof the present invention have been found to possess ground state pielectronic systems which are ideally suited for devices employing sucheffects. Furthermore, the materials of the invention may be designed soas to have the necessary charge separation in the excited state manifoldso as to result in electro-optic, SHG, and related effects ofunprecedented magnitude. The processes taught by this invention are alsoideally suited for fabrication of such devices in that extremeregularity can be maintained together with close orientation andtolerance control. Similar considerations clarify the utility of thesematerials and process in the piezoelectric, pyroelectric, waveguide, andother fields where close control of symmetry and structure are alsohighly beneficial.

DESCRIPTION OF THE PRIOR ART

Materials commonly employed in electronic, optic, electro-optic,piezoelectric, waveguide, semiconductor and similar materials areusually inorganic. Thus, perovskites such as niobates, tantalates andthe like are known for certain of such uses while glasses such as dopedsilica are known for use in others. Those skilled in the art willrecognize that many inorganic species may be employed for theelaboration and construction of these devices. See, for example, U.S.Pat. No. 3,407,309 issued to Miller; U.S. Pat. No. 3,447,855 issued toSkinners U.S. Pat. No. 3,624,406 issued to Martin; U.S. Pat. No.3,695,745 issued to Furukawa; U.S. Pat. No. 3,801,688 issued to Ballman,U.S. Pat. No. 3,874,782 issued to Schmidt, and U.S. Pat. No. 3,923,374issued to Martin.

In addition, certain species of organic materials are known for some ofthese various uses. Thus polyvinylidene fluoride is known to haveelectro-optic, SHG, and piezoelectric effects while polysiloxanes areknown for use as waveguides and piezoelectric media. In all of thesecases, however, the organic materials are known to evidence generallysmall effects; with correspondingly small effects demonstrated by thedevices employing them. The materials and processes of the presentinvention possess properties far in advance of such known materials and,therefore, are clearly distinguishable therefrom both in terms ofactivity and in terms of structure.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the polymerization of thecompositions of the invention according to the processes of theinvention whereby a mechanism is postulated. The regularity ofassemblages of monomer and the resulting polymer is shown.

FIG. 2 is a schematic representation of an electro-optic or similardevice. 1 is a dielectric or other substrate or composite substratewhile 2 is a polymer comprising the material of the invention. In thisembodiment are shown a conductor superstrate 3, control means 6, andcontacts 7 attached to dielectric or substrate 1 and conductive layer orsuperstrate 3. This arrangement allows input light signal 4 to beoperated upon by by virtue of a changing field within polymer 2generated by control means 6. Such altered or "operated" output is shownby 5.

SUMMARY OF THE INVENTION

Briefly stated, the compositions useful in the practice of the processesof the invention comprise non-linear optical and other materialscomprising one or more members of the class of chemical compounds knownas diacetylenes. Diacetylenes may be seen to possess at least twocarbon-carbon triple bonds (acetylenic bonds) at least two of whichtriple bonds are in conjugation one with another, i.e. exist in a 1-3relationship as is illustrated:

    R.sub.1 --C.tbd.C--C.tbd.C--R.sub.2                        I.

As is known to those skilled in the art, an acetylenic bond possesses agenerally linear geometry. It follows that diacetylenes possess agenerally linear arrangement of six atoms, the four carbon atomsparticipating in the diacetylenic "backbone" and each of the two atomsbonded to either end of that backbone. In addition, it is apparent thatthe diacetylenic structure is rich with electron density. Theseelectronic and geometric properties possessed by the genus ofdiacetylenes are believed to contribute to the unique suitability ofsuch compounds for inclusion in electro-optic and other compositions astaught by this invention.

Diacetylenes which are suitable for use in one or more embodiments ofthis invention conform to the general formula:

    R.sub.1 --C.tbd.C--C.tbd.C--R.sub.2                        I

where R₁ and R₂ may be the same or different and may comprise alkyl,aryl, alkaryl, or aralkyl groups having from one to about 50 carbonatoms. R₁ and R₂ may in addition, have heteroatomic substitutions orunsaturations. Thus, R₁ or R₂ may include one or more alkyl, haloalkyl,ester, alcohol, phenol, amine, nitro, amide, halogen, sulfonyl,sulfoxyl, sulfinyl, silyl, siloxyl, phosphoro, phosphato, keto,aldehyde, or other moieties. In addition, metal modifications of any ofthe foregoing may be included such as, for example, acid or phenolatesalt. In addition R₁ or R₂ or both may be ester, acid, alcohol, phenol,amine, amide, nitro, halogen, sulfonyl, sulfoxyl, silyl, siloxyl,phosphoro, phosphato, keto, aldehydo or a metal salt or phenolate. Inshort, it is contemplated that any diacetylene may be suitable for usein the practice of one or more of the embodiments of the invention withthe exception of those diacetylenes wherein R₁ or R₂ or both arehydrogen. The latter compositions are not suitable due to the fact thatthey are, in general, explosive. It is to be understood that the speciesreferred to in this description of the invention may be either straightchain, cyclic, aromatic, or branched. It should also be understood thatreference to the compositions of this invention as being diacetylenesdoes not foreclose the presence of additional acetylenic bonds therein.Thus, compositions having 3, 4, or more acetylenic bonds are foreseen aslong as at least two or more of such bonds are in conjugation one withanother. Furthermore, additional sites of unsaturation may be presentsuch as carbon-carbon, carbon-oxygen, carbon-nitrogen, or other doubleor triple bonds, aromatic or heteroaromatic species. Substitution withhalogens, hydroxyls, amines, nitros, thiols, silyls, siloxyls,phosphates, sulfates, sulfonates, or other functionalities is alsouseful.

For the practice of certain embodiments of the invention, diacetylenesmay preferably possess the general formula:

    R.sub.3 --C.tbd.C--C.tbd.C--R.sub.4                        II.

wherein R₃ is a hydrophobic chemical moiety and R₄ is a hydrophilicchemical moiety. Those skilled in the art will recognize that"hydrophobic" is a term descriptive of chemical moities or residueswhich are, in general, unattracted to water or electrically chargedspecies. Thus, hydrocarbon structures which are unsubstituted orsparingly substituted with heteroatomic functionalities are consideredhydrophobic. In contrast, a "hydrophilic" moiety species possess one ormore acid, ester, alcohol, amino, thiol, or similar heteroatomicsubstituents while hydrophobic species are characterized by asubstantial lack thereof. Of special utility in the practice of theinvention are diacetylenes of formula (II) wherein the substituent R₃comprises a hydrocarbon moiety having from one to about 30 andpreferably from 2 to about 20 carbon atoms and wherein R₄ may berepresented by the formula:

    --R.sub.5 --(A).sub.n                                      III.

where R₅ is a hydrocarbon having from one to about 50 and preferablyfrom one to about 30 carbon atoms; n is an integer from one to about 10and preferably one to three; and A is a member of the group consistingof R₆, halogen, COOH, COOR₆ CONH₂ CONHR₆, NO₂ OH, SH, NH₂, NHR₆, N(R₆)₂,silyl, siloxyl, sulfate, sulfinate, phosphate and others where R₆ is ahydrocarbon having from one to about 8 carbon atoms. Certain preferredforms of the composition include styryl moieties in the hydrocarbonportion of R₃ or include other polymerizable unsaturations such as, forexample, dienyl, vinyl or acryryl species.

Certain embodiments of the invention may usefully employ compositions ofthe formula:

    R.sub.3 --C.tbd.C--C.tbd.C--R.sub.3                        IV.

or

    R.sub.4 --C.tbd.C--C.tbd.C--R.sub.4                        V.

where R₃ and R₄ have any of the identities attributed to them above.

Additional embodiments of the invention may profitably employdiacetylenes of formula (I) where R₁ or R₂ or both have the formula:##STR1## wherein p is an integer from 0 to about 20 and preferably fromone to about 6; Y is O, NH, S, SO₂, SO₃, SiO₂, PO₃, PO₄, CH₂, amido,acetyl, acetoxy, acrylyl, methacrylyl, or styryl, and R₇ through R₁₀ maybe the same or different and may be H, NO₂, NH₂, monohalomethyl,dihalomethyl trihalomethyl, halogen, alkyl, perhaloalkyl, alkenyl, oraryl having from one to about 6 carbon atoms; SO₂, SO₃, PO₃, PO₄,siloxyl, silyl, etc. In certain preferred compositions, ethylenic groupsare included to result in styryl diacetylenic formulations.

In certain preferred compositions, centers of chirality or other formsof asymmetry may be present in the molecular structures and opticallyactive materials may be utilized for certain embodiments. Thus,materials may be utilized such as, for example, those of formula (I)wherein R₁ or R₂ or both have the formula:

    --(CH.sub.2).sub.q --R.sub.11                              VII

where q is an integer from 0 to about 20 and R₁₁ is a species having achiral or optically active center. While it is to be understood that anysubstituent having an optical center is contemplated for use herein,several exemplary embodiments may be represented by the formulas:##STR2## wherein an asterisk indicates an optical center and Ar is anaryl group. For example, Ar may be represented by either of theformulas: ##STR3## where R₇ -R₁₀ have the meanings ascribed to them inconnection with FIG. VI. In similar fashion, chiral amino acid or otheroptically active residues may be included in the diacetyleniccompositions of the invention.

As will be more fully set forth below, employment of diacetylenes havingone or more chiral centers finds preferred usage in systems requiringnoncentrosymmetry such as nonlinear optical, piezo- and pyroelectricsystems. It should be appreciated that molecules having chirality are,in general, difficult to synthesize and isolate. Thus it should beunderstood that absent a compelling reason for the synthesis of chiralspecies, such synthesis is generally avoided in the design of organicsynthetic schemes. Understanding of the physical and physiochemicalbasis for nonlinear optics as reflected in the Physical Review articleby the inventor, led to an appreciation of the desirability ofincorporating chirality in diacetylenic systems for use in thefabrication of nonlinear optical, piezo- and pyroelectric materials.Accordingly, it is believed that the inventor is the first to synthesizediacetylenes having a chiral center.

It should be apparent from the foregoing that while certain diacetylenesare preferred for certain embodiments, no limitation is intended or isto be implied with respect to the diacetylenes suitable for the practiceof one or more embodiments of this invention. All compositions whichinclude one or more chemical species having at least two acetylenicbonds, at least two of which are in conjugation one with another aresuitable.

Exemplary syntheses of diacetylenes are presented in "Synthesis ofN-(nitrophenyl)amine Substituted Diacetylene Monomers" Garito et al,Makromolecular Chemie (in press); "Synthesis of Chiral DiacetylenePolymers", Garito et al, Makromolecular Chemie (vol. 180 p. 2975, 1979);"The Chemistry of Diacetylenes", (Wiley, 1974), M. F. Shostakovskii etal; "Synthesis of Nitrophenoxymethyl Substituted Diacetylene Monomers",Kalyanaraman, Garito et al, Makromolecular Chemie, vol. 180, June 1979;"Solid State Synthesis and Properties of the Polydiacetylenes", Baughmanet al, Annals of NY Academy of Science, vol. 313 (1978); "Polymerizationof Diacetylene Carbonic Acid Monolayers at the Gas-Water Interface", Dayet al, J. Polymer Sciences, Polymer Letters ed. vol. 16, p. 205 (1978);and U.S. Pat. No. 3,923,622 issued to Baughman et al.

As a class, diacetylenes exhibit uniquely regular structures in thinfilms, multi-layer films, and polymers formed therefrom. In thin filmsformed on substrates, diacetylenes assume a regular orientation. Thisphenomenon which is illustrated in FIG. 1 is known. See "Kinetics ofThermal Polymerization in the Solid State2,4-Hexadiyne-1,6-Diol-Bis(p-Toluene Sulfonate), Garito et al, J.Polymer Sci. 16, 335-338(1978); "Kinetics of Solid State Polymerizationof 2,4-Hexadiyne-1,6-Diol-Bis(p-Toluene Sulfonate)", Garito et al,Molecular Metals, Hatfield ed. (Plenum, 1979); Wegner "Recent Progressin the Chemistry and Physics of Poly(diacetylenes)", Molecular Metals,W. E. Hatfield ed. Plenum (1979). Additional reports are contained inJournal of Polymer Science, Polymer Chemistry ed., vol. 17, pp.1631-1644 (1979) "Polymerization of Diacetylenes in Multi-Layers" byWegner et al; and Macromolecular Chemistry, vol. 179, pp. 1639-1642(1978) "The Quantum Yield of the Topochemical Photopolymerization ofDiacetylenes in Multi-Layers" by Wegner et al; "Solid-StatePolymerization of a Nitrophenoxy Disubstituted Diacetylene", Garito, etal. Makromolecular Chemie (in press). Reference is specifically made tothese reviews and to the references cited therein. Wegner reports on thechemistry, synthesis, structure, orientation and polymerization ofdiacetylenes and poly(diacetylenes) and describes the multi-layerbehavior of certain species thereof. The regular orientation in a thinfilm has been reported to be in a "herringbone" array. The arrays may bequite large and may, it is believed, extend over the entire area of thefilm. Wegner has observed large domains thought to be formed of areas ofregular orientation. It is possible to form single domain films whichcan polymerize into single domain polymers.

The chemical molecular structure of such polymers, while not entirelyclear, is subject to interpretation. As shown in FIG. 1, polymers ofdiacetylenes are believed to possess triple and double bonds in a 1-3relationship in the subunits of the polymer. It will be understood bythose skilled in the art that the two "resonance structures" indicatedfor the polymer represents in fact that, with poly(diacetylenes) as withmost organic molecules, structural description in terms of bond orderi.e., triple, double etc. is less than precise. Thus, with theunderstanding that the polymers possess bond characteristics which arenot fully representable as any one single structure, such polymers willbe described as having a repeating subunit wherein four carbon atoms arealigned in a generally linear configuration.

Thus, the polymers produced according to the practice of this inventionmay be alternatively described as (1) being substantially regular inorientation, at least within any polymer domain; (2) having anacetylenic bond in the subunit structure thereof, or (3) possessingsubunits which have four carbon atoms in a generally linearconfiguration.

According to a preferred practice of the invention, substrates arecoated with diacetylenic compositions. These coatings may be elaboratedin such a fashion that high regularity and periodicity of structureresults such as is illustrated in FIG. 1. Such coating of substrateswith diacetylenic compositions is preferably accomplished by theLangmuir-Blodgett technique. This technique, which is well known tothose skilled in the art, causes a thin film of diacetylene to bedeposited upon the surface of a fluid. The surface layer is thencompressed to minimize the surface area occupied by the diacetylene soas to effect a closest packing arrangement thereof. This closely packedand arrayed diacetylenic composition is then transferred to a substrateby dipping. The use of diacetylenes having hydrophobic and hydrophilicsubstituents on either end thereof facilitates the use of the technique.Multi-layers may be built up sequentially by this technique. Thesemulti-layers may be uniform in composition or may be dissimilar. Theymay number from two to several hundreds and may, thus, comprise thin orthick films.

Alternative means of placing diacetylenes on substrates may be utilizedas well. Thus, the "whirling" or spinning technique as described in theDeForest reference, roller coating as is currently practiced in the art,or even dipping may be employed so to apply the diacetylenic species tothe substrate. Coating by vapor deposition may also be employed.

The regularity which may be accomplished in the establishment of filmsor coatings of diacetylenes according to a preferred practice of thisinvention may carry over to the polymers formed therefrom. In FIG. 1,the geometry of the arrays of monomeric diacetylenes which may beestablished is very nearly the same as the geometry of the subsequentlyformed polymers. In an exemplary case, the difference in orientationgeometry is less than 5 degrees. This fact coupled with the nearly idealorientation of polymerizable moieties with regard to each other and theconcommitantly excellent polymerization yields efficiently contribute tothe overall regularity in the polymerized species which are thus formed.

As will be readily apparent to those skilled in the art, the extremeregularity which is possessed by these polymers extends not only togeometric and steric regularity, but also to electronic andcompositional regularity as well. Thus, polymers formed from monomerswith a given functionality or feature present therein will exhibit thisfunctionality or feature on a substantially periodic basis throughoutthe polymer. Similarly, due to this regularity, polymer films oncoatings may be formed which have uniform dimensions, especially uniformthicknesses. A further manifestation of the unique structure of thesepolymers is the electronic regularity occuring therein. Thus thealternating double and triple bonds which (according to one viewpoint)occurs in the "backbones" of the polymers combines with the regularityof the backbones inter se, it is believed, to result in a uniquelyregular pi electronic density associated with the polymer. All of thesefactors are thought to contribute to the extreme suitability of thepolymers of this invention for the electronic, electro-optic and otheruses taught hereby.

The materials of this invention may be employed otherwise than in thinfilms to result in electronic, electro-optic and other devices. Thussingle crystals of the diacetylenic materials disclosed herein may begrown by any of the techniques known to those skilled in the art; thosecrystals may be designed to exhibit many of the properties shown by thinfilm devices. Thus single crystals having extremely high electrooptic,electroacoustic, SHG, piezoelectric, and pyroelectric effects may beformulated.

The compositions useful in the practice of the invention may includespecies in addition to the aforedescribed diacetylenes. Thus, additionalpolymerizable materials may be added as may catalysts, sensitizers,pigments, dyes, filters and dopants. Additionally, organic or inorganicmaterials may be included to alter the electrical properties of thecompositions. The additional polymerizable materials which may beincluded may encompass any of the wide variety of polymerizable speciesknown to those skilled in the art. Olefinics such as vinyl, styryl,acrylic, dienyl, etc. are preferred. Of these, dienyl and acrylicspecies are most preferred. Dimers of nitroso compounds may also beincluded to modify the polymerization behavior. The composition may,optionally, contain a sensitizer or catalyst to improve thephotochemical interaction between the monomeric compositions andincident radiation. Such sensitizers are well known in the art andinclude, for example, acetophenone, acyloin derivatives, benzophenone,dyes such as indigo derivatives and many other species. The sensitizersmay be included in amounts up to about 5% by weight of composition andpreferably between about 1% and about 3%. In an alternative embodiment,one or more layers of diacetylenic composition may be "sandwiched" withlayers of sensitizer-containing formulation to give good results.

Other compositions may include polymerizable sites in the diacetylenicspecies in addition to the diacetylenic bonds themselves. Thus,diacetylenic compounds having acrylic, styryl, vinyl or otherpolymerizable functionalities may be used to good result. In such acase, the polymerization of such additional polymerizable structures maybe accomplished concomitantly with or subsequent to the polymerizationof the "backbone" diacetylenes. In cases where multiple single layers oforiented diacetylenes are laid down upon a substrate, it may be seenthat polymerization of the "backbone" may occur almost exclusivelywithin one layer. The presence of other polymerization or crosslinkingagents may result in interlayer linking to yield useful materials. Theinclusion of styrene residues is especially preferred for this purpose.

Polymerization of the layers, coatings, arrays or crystals of thediacetylenes taught hereby may be accomplished in any of the ways whichare well known to those skilled in the art. Thus, simple heating,preferably with a radial initiator present in the formulation, orphotoinitiation, either with or without a sensitizer is suitable. Thelatter procedure is preferred due to the ability of those skilled in theart to polymerize selectively those portions of the whole which aredesired to be polymerized without substantial polymerization of otherareas. In this regard, reference is made to Ser. No. 052,007 of whichthis application is a continuation in part and to Ser. No. 113,552)which is copending with this application and which has been incorporatedherein by reference. This ability facilitates the microfabrication ofthin film patterns in ways analogous to those employed inphotolithography. Such patterns of polymer which display electronic,electro-optic, waveguide or other properties may be employed in numerousmicrocircuitry and other applications as will be apparent to thoseskilled in the art. Macroscopic use is, of course, also forseen andintended hereby.

As has been indicated, electro-optic, electro-acoustic, SHG, and relatedeffects employ diacetylenic materials which are crystallizable intocrystals having a noncentrosymmetric unit cell. It is further to beconsidered that the accomplishment of higher degrees of asymmetry are,in general, rewarded with materials and devices having higher degrees ofnon-linear optic effect as long as a suitable electronic structure ismaintained. Some of the diacetylenes which exhibit the most pronouncedelectro-optic and other nonlinear optic effects are those which includeone or more chiral centers. Thus diacetylenes according to Formula (I)wherein R₁ or R₂ or both have the Formula (VII) are preferred. As willbe appreciated by those skilled in the art the degree of asymmetrypresent in a chiral molecule will vary as the substitution pattern onthe asymmetric center varies. Especially useful materials have beenformulated having two or more chiral centers, either one or both ends ofthe diacetylenic core. Examples of chiral diacetylenes which arepreferred for nonlinear optical uses are represented by the formulas:##STR4## while a preferred diacetylene having two such groups isrepresented by the structure: ##STR5## These and numerous other chiraldiacetylenes which may form crystals having a non-centrosymmetric unitcell for use as nonlinear optical, piezo-, and pyroelectric materials.

Noncentrosymmetric diacetylenic molecules which do not have chiralityare also suitable for use in one or more nonlinear optical or relatedsystems. Thus, any diacetylene species which has no center of inversionsymmetry may be employed. One such preferred material for electro-opticand SHG purposes is represented by the formula: ##STR6## Such materialand its analogs have been found to be highly asymmetric on both themolecular and unit cell level and have demonstrated high electro-opticcoefficients. Other asymmetric diacetylenes are similarly useful.

Many of the diacetylenes which may be employed in non-linear opticsystems, i.e. those which are crystallizalable into crystals havingnon-centrosymmetric unit cells, may evidence second harmonic generationwhich is phase matchable. Phase matchability, which has been explainedabove, makes these materials extremely well suited for use as SHG media.While at the present time it has not been possible to predict which ofthe diacetylenes will exhibit phase matchability, routineexperimentation will identify members of the class. The suitability ofthe diacetylenes of this invention for use as phase matchable secondharmonic generating media is easily ascertained. Diacetylenes which areto be tested are powdered and exposed to laser light. The secondharmonic generation shown by the diacetylene species is compared to aninternal standard, lithium iodate, and qualitatively evaluated. Thisprocedure, which is well known to those skilled in the art disclosesthat many of the diacetylenes are superior to the standard. Furtherexemplary species among these are: ##STR7## Numerous others are, ofcourse, also suitable. Those molecules identified as XIV to XVII arebelieved to exhibit phase matchability and, accordingly, representpreferred material for SHG use. It is expected that large numbers ofadditional diacetylenes will also be so identified.

As has been explained, those materials which are useful forpiezoelectric and pyroelectric applications share symmetry requirementswith nonlinear optical systems and, hence, must possess no center ofinversion symmetry. It will be understood that appreciable piezo- andpyroelectric effects can be exhibited by those diacetylenes havingnoncentrosymmetry without regard to the electronic nature of thespecies. Such materials therefore encompass all of those diacetyleneswhich are noncentrosymmetric on a crystalline unit cell basis, and allsuch diacetylenes may be predicted to exhibit piezo-, or pyroelectricactivity.

For use as waveguides diacetylenes according to this invention are notconstrained in terms of symmetry. For waveguiding purposes it isnecessary only that the diacetylene have a regular physical structureand uniform index of refraction. According to preferred practice, layersof diacetylenic material may be built up into waveguides or otherstructures having definite dimensions by use of the Langmuir-Blodgettmethod and other techniques. Those skilled in the art will appreciatethat the index of refraction of a diacetylenic composition will varydepending upon the diacetylene moieties chosen for inclusion therein.Thus, layers of uniform thickness of differing diacetylenic species maybe deposited upon a substrate and, preferably, subsequently, polymerizedto result in planar waveguides of high efficiency. By virtue of theextreme regularity which is present in the diacetylene monomers andpolymers as taught herein, waveguides having very low loss rates arepossible. Of course, discetylene layers may be bounded by non-diacetylnelayers to result in planor waveguides as long as the boundry layers havea lower index of rejection than the diacetylene layer.

Those skilled in the art will readily recognize that the variousembodiment of the present invention may be combined to yield devices ofgreat flexibility and use. The waveguiding properties of thediacetylenes may be combined with the nonlinear optical properties sothat a guided light wave can be operated upon electro-optically or thelike. In a similar fashion, piezoelectric properties may be designedinto a waveguide so that, for example, a physical motion may be coupledto a propagated light wave. Indeed, large arrays of nonlinear optical,piezoelectric, semiconductor and other devices may be formed within awaveguiding system so as to result in assemblies of devices of diversecharacter and use. It will be apparent to one skilled in the art that,in such fashion, miniaturized electro-optic logic networks mayconveniently be established. Such materials are useful on a macroscopicscale as well. Thus piezoelectric or pyroelectric arrays may be had insheet or film form which may have dimensions on the order of meters. Itwill be apparent that numerous other macroscopic uses are also possiblefor such systems.

For certain applications, it is highly beneficial to provide a strongadherence of the coatings to the underlying substrate. It has been foundto be possible to bond such coatings to substrates covalently utilizingcertain techniques. Thus, hydroxyl or other functional groups commonlyfound on the surfaces of substrates may be utilized to consummate silylor siloxyl linkages with a suitably silicon substituted diacetylenicspecies. See E. P. Plueddemann "Mechanism of Adhesion Through SilaneCoupling Agents" in Composite Materials, Brautman; Krock eds, vol. 6,ch. 6, Academy Press (1974). Other means of covalently bonding film tosubstrates or of film precursor species to substrates will readily occurto those skilled in the art. Thus, it is desirable to coat the substratewith a composition which may form covalent linkages with such substrateand which may also form covalent linkages with the diacetylenic specieswhich comprise the nonlinear optical or other layers. While anycomposition which will form covalent bonding may be employed, preferredspecies for accomplishing such covalent bonding may be represented bythe formula:

    (HO--R.sub.12).sub.3 --Si(R.sub.13)Z                       XX

where the R₁₂ groups may be the same or different and are hydrocarbylgroups having from one to about six carbon atoms, where R₁₃ is ahydrocarbyl group having from one to about six carbon atoms, and Z isany substituent which may covalently bond with the diacetylenic specieof choice. Preferably, Z is an amine, and is used to form an amidelinkage with a carboxyl group on the diacetylene, but any suitablesubstituent may be employed. One such exemplary composition is3-aminopropyltriethoxysilane which is described by Formula XX when R₁₂is ethyl, R₁₃ is propyl and Z is amino. It will be understood thatcovalent bonds other than the siloxyl and amide bonds described abovemay be satisfactorily employed in the practice of the invention.

The fabrication of articles employing the novel materials and processesof this invention is not complex. Those skilled in the art willrecognize that single crystals of suitable diacetylenic species may begrown employing an appropriate solvent recrystallization system. Thus,for example either of the materials XVII or XIX may be recrystallizedfrom a polar solvent such as nitromethane in manners well known to thoseskilled in the art to yield satisfactorily large single crystals. Toemploy such single crystals in the generation of second harmonics it isnecessary only to pass intense laser light through such crystals. Thegeneration of second harmonics will occur spontaneously within thecrystals and a mixture of fundamental and doubled frequencies willemerge. A conventional filter designed so as to filter out thefundamental frequencies is helpful in isolating and identifying thesecond harmonic. It will be appreciated by those skilled in the art andupon perusal of the Kaminow work cited previously, that such secondharmonic may be generated over a spectrum of laser frequencies with butsmall changes in efficiency. It is, in general, necessary only that themedium be transparent to both the fundamental frequency and its secondharmonic.

The electro-optic and other nonlinear optical effects may be evidencedby single crystals formed of the diacetylenic materials taught by thepresent invention. Thus, a single crystal of, for example, either of thematerials XVII or XIX may be fitted with electrical contacts onappropriately located (generally parallel) crystal faces or otherwiseadapted with means for generation of an electric field within suchcrystal. Passage of intense laser light through the crystal at a timewhen the electric field is being modulated by a suitable control meanswill result in a modulation of the light signal. It will be appreciatedthat the crystal must be transparent to both the incident and exit lightfrequencies. Those skilled in the art will further appreciate that othernonlinear optical phenomena may be accomplished in a similar wayemploying single crystals of suitable diacetylenes. All of these usesmay also be accomplished through the employment of films of diacetyleneseither polymerized or not.

The use of single crystals for piezoelectric and pyroelectric deviceshas long been known in the art; such may be accompanished withdiacetylenes as well. Thus, it is necessary only to grow a crystal of asuitable diacetylene such as, for example, XVII or XIX and to fit thecrystal with a means for the establishment of an electrical potentialacross opposite faces of such crystal to construct a piezoelectric orpyroelectric device from the materials and processes of the presentinvention.

To formulate waveguides from the diacetylenes of the present invention,a thin film of diacetylenic material is elaborated on a substrate, whichsubstrate has an index of refraction less than the index of refractionof the film. Additionally, a superstrate, also having an index ofrefraction less than the index of refraction of the film, is placed ontop of the film. Thus, it may be seen that there is a layer ofdiacetylenic material bounded by two other layers having indices ofrefraction less than the index of the diacetylenic layer. For mostapplications, the diacetylene may preferably be polymerized to yieldwaveguiding structures of high physical integrity. A preferred form ofsuch waveguide employs covalently bonding species such as theaforementioned silane bonding species between the film and either orboth of the substrate and superstrate. Since the siloxanes which resultfrom this process have indices of refraction which are, in general, lessthan the indices of refraction of the polydiacetylenes, the waveguidingrequirements are maintained. Additionally, it will be readilyappreciated that such covalent bonding adds materially to the coherencyand strength of the aggregate waveguide. In the alternative, it ispossible to build up plurality of layers of diacetylenes and/ordiacetylenes modified with other species to result in suitablewaveguiding combinations. It will further be appreciated that suchwaveguides are most useful when the diacetylenes have been polymerizedinto polydiacetylenes, thus, to evidence the desired coherency andstrength. Those skilled in the art will recognize that for employment ofwaveguides according to the present invention it will be necessary tocouple light into and out of the guide. For this function are known manycoupling means such as prism couplers, grating couplers, and directimpingement devices. As will also be appreciated by those skilled in theart, light waves being propagated by waveguide according to the presentinvention may be operated upon by electro-optic, SHG, other nonlinearoptic, piezoelectric, and other devices which are included in one ormore sections or segments of the guide. According to one embodiment,electro-optically functional waveguides formed of the diacetylenes ofthis invention may be laid down upon a substrate which is semiconductingto yield useful devices.

Waveguides made according to the above general description may beformulated from materials which have electro-optic, SHG, other nonlinearoptical, piezoelectric, pyroelectric, or other properties. Thus, aplanar waveguide may be also a nonlinear optic device. For such use, itis necessary only that the diacetylenic film comprise a diacetylenewhich exhibits nonlinear optical or other properties. Thus, a waveguidewhich is formulated from, for example, the material XIV will not onlyguide laser light, but will also generate second harmonics or may befitted with field generation means for electro-optically operating uponsuch laser light. It will be readily appreciated that complex aggregatesof electro-optics, piezoelectric, and other devices may be placed inlarge waveguiding arrays so as to perform complex integrated systems foroperating upon light. Thus, an optic logical device may be soelaborated.

Piezoelectric and pyroelectric devices may also be developed employingthin film structures. Thus, thin film structural aggregates fitted withthe appropriate electrodes may be used as piezoelectric and pyroelectriccomponents.

In the elaboration of these thin film devices, the Langmuir-Blodgettfilm making technique is frequently preferred. Photolithographicprocesses as described in Ser. No. 133,552 are convenient forelaborating arrays of components. Other methods such as spinning, orvapor coating as described hereinbefore may also be used. These latterprocedures are especially useful for the elaboration of thin filmwaveguides.

The following examples are intended to illustrate certain preferredcompositions and processes according to the instant invention. Copendingapplication Ser. No. 113,552 which specification has been incorporatedherein by reference, presents other examples which are pertinent to thepractice of one or more embodiments of the present invention.

EXAMPLE 1 Synthesis of Diacetylene alkyl-acid monomersPentacosa-10,12-diynoic acid

Diacetylene alkyl-acid monomers for use in mono- and multilayerpreparations were synthesized by the Chodkiewicz coupling procedureusing bromoacetylenes prepared following Strauss. See Chodkiewics W.Ann. Chem. (Paris) 2, 853 (1957) and Strauss, et al, Ber. 633, 1868(1930. For example, 1-bromo undecyn-10-oic acid was coupled totetradecyne to form pentacosa-10,12-diynoic acid. 50 mmol of tetradecynedissolved in 5 ml ethanol was added with stirring to a 50 ml ethanolsolution of 100 mmol hydroxylamine hydrochloride, 10 mmol Cu Cl and 200m.mole of ethylamine forming a yellow solution. The stirred solution wascooled to 1° C. and 50 m.moles of 1-bromo-undecyn-10-oic acid dissolvedin 60 ml ethanol was added dropwise over 30 minutes while thetemperature was maintained at 15°-20° C. After the addition was completethe reaction mixture was stirred for 3 hours at 15°-20° C. The mixturewas then acidfied to pH 1 and extracted twice with 100 ml ethyl acetate.The organic layer was separated, dried over magnesium sulfate, filteredthrough fluorosil and evaporated to give a colorless, viscous oil. Theoil was taken up in methanol-petroleum ether and the solution wasfiltered. Upon cooling of the filtrate, pentacosa-10,12-diynoic acidcrystallized as colorless platelets (m.p. 59°-60° C.). The plateletsbecome an intense blue upon standing in laboratory light for a shorttime.

EXAMPLE 2

The apparatus used for multilayer preparation consists of a Langmuirtrough made of Teflon with dimensions of 12.2×30 cm area and 2 cm deep.The surface pressure is applied by a movable Teflon barrier connected toa motor driven screw gear. A Wilhelmy balance is used continuously tomeasure the surface pressure. The solid substrate is connected to avibration-free solid rod and moved in and out of the trough using areversibly geared motor at speeds of 1-3 cm/hr.

A 4×10⁻³ M solution of pentacosa-10,12-diynoic acid in n-hexane wasspread on a 1×10⁻³ M solution of cadmium chloride in water. The pH ofthe CdCl₂ solution was previously adjusted to 6.1 using sodiumbicarbonate. Successive layers were deposited on the solid substrates,at a constant surface pressure of 15 dyne per cm with a dipping speed of0.5 mm/sec. Surface pressure area curves show that near 23° C. and asurface pressure of about 15 dyne/cm, a monomer molecule occupies 20A² ;Y type deposition of the layers was observed.

EXAMPLE 3 Preparation of a covalently bound diacetylene on a siliconsurface

Silicon plates with an oxide layer 100μ thick were immersed inconcentrated nitric acid for two hours. After rinsing with water, thewater contact angle (αw) was determined to be 44° C. After thoroughdrying, the plates were treated with vapors of 3-aminopropyltriethoxysilane. The substrate was placed above a boiling solution of 2ml of the silane in 100 ml dry p-xylene under nitrogen for 16 hours. Thesubstrate was bathed in the vapor, the vapor condensing 5 cm above thesubstrate. The substrate was rinsed in absolute ethanol and water, αwwas determined to be 45° C. The silanated substrate was immersed in asolution of 22 mg (0.06 mmol) of 10,12-pentacosadiynoic acid in 10 mlanhydrous pyridine. A solution of 14 mg (0.07 mmol) ofN,N-dicyclohexylcarbodiimide in 1 ml pyridine was added. The wafers weretreated for 16 hours at room temperature under nitrogen. The substratewas rinsed with pyridine, ethanol, boiling pyridine, and boiling ethanoland dried. The αw was determined to be 78° C.

EXAMPLE 4 Preparation of N-d(+)(α-methylbenzyl)-10,12-pentacosadiynamide

To a solution of 510 mg (1.36 mmol) of 10,12-pentacosadiynoic acid in 10ml tetrahydrofuran was added 138 mg (1.36 mmol) of triethylamine. Theresulting cloudy solution was cooled to 0° C. and 129 mg (1.36 mmol) ofmethyl chloroformate was added dropwise over 1 min. A white solid formedimmediately upon addition. The mixture was stirred 1 hour at 0° C., then165 mg (1.36 mmol) of d(+)-α-methylbenzylamine was added and the mixturewas heated at reflux for one hour. Gas evolution was evident within fiveminutes of addition, and ceased after 15 minutes. The mixture was cooledto room temperature and filtered. The filtrate was washed with 10 mlportions of 1M HCl, water, and saturated aqueous potassium bicarbonatesolution, and dried over (MgSO₄). Evaporation yielded 540 mg (83% crudeyield) of a white solid. Recrystallization from ether-petroleum ethergave white crytals, m.p. 65.5°-66.5° C. IR film: 1470, 1545, 1640, 1860,1925, and 3310 cm⁻¹. [α]D³¹ (CHCl₃)=44° C.

EXAMPLE 5 Preparation ofN,N'-bis-(α-methylbenzyl)-10,12-docasadiyndiamide

To a solution of 725 mg (2.00 mmol) of 10,12-docasadiyndioic acid in 50ml THF was added 405 mg (4.00 mmol) of triethylamine. The solution wascooled to 0° C. and 378 mg (4.00 mmol) of methyl chloroformate was addeddropwise over one minute. The resulting white mixture was stirred onehour at 0° C., and 485 mg (4.00 mmol) of d(+)-α-methylbenzylamine wasadded. The reaction mixture was heated at reflux for one hour (gasevolution began immediately upon amine addition and ceased after 20minutes). The mixture was cooled to room temperature and filtered. Thefiltrate was washed with 25 ml portions of 1M HCl, water, and saturatedaqueous sodium bicarbonate solution and dried over (MgSO₄). Evaporationyielded 842 mg (74% crude yield) of a white solid, which polymerizedrapidly upon exposure to UV light. Recrystallization fromether-petroleum ether gave 456 mg of white crystals, m.p. 87.5°-89° C.;IR (film): 1530, 1635, 2850, 2920, and 3300 cm⁻¹.

EXAMPLE 6 Preparation of 11-bromo-10-undecynoic acid

To a solution of 36.45 g (200 mmol) of 10-undecynoic acid in 200 ml 1NNaOH at 0° C. was added a solution of alkaline sodium hypobromitedropwise over 30 minutes, maintaining the temperature below 5° C. (thehypobromite solution was prepared by the dropwise addition of 35.16 g(220 mmol) of bromine to 55 ml of 20N NaOH at 0°-5° C.). The mixture wasstirred four hours at 0°-5° C., and was then acidified to pH 1 with 9MH₂ SO₄. The solution was extracted with three 150 ml portions of ether.The combined extracts were dried (Na₂ SO₄) and evaporated yielding50.159 (96% crude) of a pale yellow solid. This was used without furtherpurification.

EXAMPLE 7 Preparation of N-(α-methylbenzyl)-11-bromo-10-undecynamide

To a solution of 2.612 g (10 mmol) of 1-bromo-10-undecynoic acid in 100ml THF was added 1.012 g (10 mmol) of triethylamine. The solution wascooled to 0° C. and 0.945 g (10 mmol) of methyl chloroformate was addeddropwise over 3 minutes. The resulting cloudy white mixture was stirred1 hr. at 0° C., then 1.212 g of d(+)-α-methylbenzylamine was then added.The resulting mixture was heated to reflux 1 hour (gas evaporation beganwithin 5 minutes of addition and ceased after 20 minutes). The mixturewas cooled to room temperature and filtered. The filtrate was washedwith 50 ml portions of 1N HCl, water, and saturated aqueous potassiumbicarbonate solution and dried over (MgSO₄). Evaporation gave 3.217 g(88% crude yield) of a pale yellow solid. IR (film): 1450, 1540, 1640,2860, 2940, and 3300 cm ⁻¹.

EXAMPLE 8 Preparation ofN-(α-methylbenzyl)-14-hydroxy-10,12-tetradecadiynamide

To a solution of 20 mg (0.10 mmol) of cuprous chloride, 175 mg (2.50mmol) of hydroxylamine hydrochloride, and 980 mg (21.7 mmol) of 70%aqueous ethylamine in 5 ml water was added 981 mg (17.5 mmol) ofpropargyl alcohol. The resulting yellow mixture was stirred 5 minutes atambient temperature, and a solution of 911 mg (2.50 mmol) ofN-(α-methylbenzyl)-11-bromo-10-undecynamide in 20 ml DMSO was then addeddropwise over 20 minutes. The mixture was stirred 3 hours at ambienttemperature (the solution became clear after 1 hour) and then wasacidified to pH 1 with concentrated HCl. The solution was extracted withthree 75 ml portions of ethyl acetate. The combined organic extractswere washed with two 100 ml portions of water and two 100 ml portions ofbrine and dried over (MgSO₄). Evaporation gave 815 mg of a viscous paleyellow oil. NMR indicated a mixture of approximately 1:1 starting amideand coupled hydroxyamide. The product was purified by columnchromatography (silica gel, 60% ether-hexanes as eluent), affordingstarting amide R_(f) 0.45, 80% ether-hexanes) and 220 mg of a colorlessoil (R_(f) 0.15, 80% ether-hexanes).

EXAMPLE 9 Preparation ofN-(α-methylbenzyl)-14-(2,4-dinitrophenoxy)-10,12-tetradecadiynamide

To a solution of 220 mg (0.65 mmol) ofN-(α-methylbenzyl)-14-hydroxy-10,12-tetradecadiynamide in 10 ml DMSO wasadded 506 mg (5.00 mmol) of triethylamine. To the solution was thenadded 130 mg (0.70 mmol) of 2,4-dinitrofluorobenzene. The resulting redsolution was stirred 16 hours at ambient temperature, and 25 ml ofsaturated aqueous potassium bicarbonate solution was then added. Afterstirring 15 minutes, the mixture was poured into 100 ml of water and theresulting solution was extracted with 100 ml portions of ethyl acetate.The combined organic extracts were washed with three 50 ml portions ofwater and three 50 ml portions of saturated aqueous sodium bicarbonatesolution and dried over (MgSO₄). Evaporation gave 312 mg of a red oil.NMR indicated no starting alcohol was present. The product was purifiedby passing it through silica gel (ether as eluent); crystallization fromether petroleum ether gave white crystals, m.p. 59°-60° C. NMR (CDC₁₃):9.42-7.30, m, 8H aryl H's; 6.00, br s, 1H, N--H; 5.10, br s 2H, O--CH₃C═C and m, 1H, CHCH₃ ; 2.30, m, 4H, C═CH₂ CH₂ and --CH₂ CO--; 1.55, d,J=7 Hz, 3H, CH₃ and 170--1.20, m, 12 H, other CH₂.

EXAMPLE 10 2,4-Hexadiyn-1,6-diol-bis-(2,4-dinitrophenyl)ether

To a solution of 2,4-hexadiyn-1,6-diol (1.1 g) in acetone (15 ml), K₂CO₃ (0.5 g) was added. To the stirred solution at room temperature,2,4-dintrofluorobenzene (3.8 g) was added gradually and the dark redsolution stirred overnight at room temperature. It was poured intoexcess water, the pale yellow solid filtered off, washed with water anddried. Recrystallization from dioxaneethanol gave short, light pinkneedles, m.p. 210° C., (4.2 g., 95%). IR (KBr): 1592, 1333, 834(Ar--NO₂)cm⁻¹.

EXAMPLE 11 N-(2-Propynyl)-2,4-dinitroaniline

To a suspension of potassium carbonate (1.0 g) in acetone (10 ml) wasadded 2-propyn-1-amine (0.26 g, 473×10⁻³ mole). 2,4-Dinitrofluorobenzene(1.32 g, 7.10×10⁻³ mole) was gradually added with stirring and thereaction mixture was refluxed two hours. After cooling it was pouredinto excess water and filtered. Recrystallization of the crude solidfrom ethanol afforded yellow needles; m.p. 151°-152° C. Yield: 0.99 g(95%). IR (KBr): 3367 (NH), 3268 (═CH), 1618, 1590, 1333 and 1311 cm⁻¹(Ar--NO₂).

EXAMPLE 12 N,N'-Bis-(2,4-dinitrophenyl)-2,4-hexadiyn-1,6-diamine

To a suspension of Cu(OAc)₂.H₂ O (1.5 g) in pyridine-methanol (1:1, 10ml) was added N-(2-propynyl)-2,4-dinitroaniline (1.00 g, 4.52×10⁻¹mole). The reaction mixture was stirred at 50° C. for 30 minutes. Themixture was poured into excess water, and filtered. The crude solid wasrecrystallized from nitromethane to afford pale green crystals. Yield:0.86 g (86%). The compound failed to melt at 200° C. but changed fromgreen to bronze color at 120° C. It could be recrystallized from dioxaneto give a different crystal form, appearing as orange crystals whichturn deep orange at 140° C. IR (KBr): 3380 (NH), 1617, 1592, 1333 and1312 cm⁻¹ (Ar--NO₂).

EXAMPLE 13 6-Hydroxy-2,4-hexadiynyl-1-(4-nitro-2-trifluoromethyl)aniline

To a suspension of Cu(OAc)₂.H₂ O (89.6 g, 4.49×10⁻¹ mole) inpyridine-methanol (1:1, 500 ml) at 0° C., was addedN-(2-propynyl)-4-nitro-2-trifluoromethylaniline (5.01 g, 2.05×10⁻² mole)and 2-propyn-1-ol (2.76 g, 4.91×10⁻² mole. Additional 2-propyn-1-ol(20.83 g, 3.72×10⁻¹ mole) was dissolved in methanol (25 ml) and addeddropwise over 6 hours as the reaction was gradually allowed to warm toroom temperature. The reaction mixture was stirred for an additional 1hour and poured into water (3500 ml). Filtration gave a pink solid thatwas chromatographed on a silica column, eluting with chloroform, to givea pale yellow solid. Recrystallization from toluene-petroleum ether gave1.96 g, (32%) m.p. 142°-144° C. I.R. (KBr): 3480 (NH), 3460 (OH), 1583(Ar--NO₂) and 1307 cm⁻¹ (CF₃).

EXAMPLE 14 Synthesis of6-(2,4-dinitrophenoxy)-2,4-hexadiynyl-1-(4-nitro-2-trifluoromethyl)aniline

6-hydroxy-2,4-hexadiynyl-1-(4-nitro-2-trifluoromethyl)aniline (1.00 g,3.36×10⁻³ mole), K₂ CO₃ (2 g), triethylamine (1 ml), anddinitrofluorobenzene (3.00 g, 1.61×10⁻¹ mole) were refluxed in acetone(30 ml) for 4 hours and stirred at room temperature for 12 hours. Thereaction mixture was poured into water (300 ml) and extracted with ethylacetate. The ethyl acetate solution was washed with saturated aqueoussodium bicarbonate solution, then water, and dried over magnesiumsulfate, filtered and evaporated. The residue was chromatographed on asilica column, eluting with chloroform to give crude product. This wasthen rechromatographed on a silica column eluting with toluene to giveproduct as a pure solid (one spot by TLC on silica with 1:3 ethylacetate-chloroform). Recrystallization from toluene-petroleum ether(hot) gave a pale yellow solid (1.25 g, 80%) m.p. 184°-185° C. (withdecomposition). ¹ H NMR (acetone-d₆ -DMSO-d₆):=4.35 (d:2H, J= 6 Hz),5.18 (s:2H), 6.50-8.75 (m:7H).

EXAMPLE 15 6-Chloro-2,4-hexadiynyl-1-(2,4-dinitro)analine

A solution of 6-hydroxy-2,4-hexadiynyl-1-(2,4-dinitro)aniline (0.99 g,3.60×10⁻¹ mole) in dry pyridine (5 ml) was cooled in an ice bath and asolution of p-toluene sulfonyl chloride (3.34 g, 1.75×10⁻² mole) inpyridine (5 ml) was added dropwise. The reaction mixture was kept at 0°C. for 5 hours. At the end of this time, the reaction mixture was pouredinto water (300 ml), acidified with aqueous HCl (30%) and extracted withchloroform. The chloroform layer was washed with aqueous saturatedsodium bicarbonate then dried over sodium sulfate, filtered andevaporated. The residue was chromatographed on a silica column, elutingwith chloroform and recrystallized from benzene-petroleum ether to give0.33 g, (31%) as pale yellow crystals, m.p. 122°-123° C. I.R. (neat):3345 (NH, 1605 and 1587 cm⁻¹ (Ar--NO₂).

EXAMPLE 166-(4-Nitrobenzoyl)-2,4-hexadiynyl-1-(4-nitro-2-trifluoromethyl)aniline

To a solution of6-hydroxy-2,4-hexadiynyl-1-(4-nitro-2-trifluoromethyl)aniline (0.14 g,4.70×10⁻⁴ mole) and 4-nitrobenzoyl chloride (0.21 g, 1.13×10⁻³ mole) inmethylene chloride (50 ml) was added triethylamine (1 ml). The reactionmixture as refluxed for 90 minutes. After cooling the mixture was pouredinto water (250 ml) and extracted with saturated aqueous sodiumbicarbonate, then water, dried over magnesium sulfate, filtered andevaporated. The resulting oil, was crystallized from toluene andrecrystallized from toluene-petroleum ether to afford the ester as whitecrystals (0.15 g, 71%) m.p. 160°-161° C.

I.R. (nat): 3435 (NH), 1730 (C═O), 1610, 1588 (Ar--NO₂), 1305 (CF₃),1261 (C--O), and 1112 cm⁻¹ (--O--CH₂ --C).

EXAMPLE 17 Synthesis of 1,22-(l-dinitrophenylalanyl)-10,12-docosadiyne

To a solution of N-dinitrophenyl-l-alanine (0.166 g) and 0.104 gm of10,12 docosadiyne-1,22 diol in 10 ml of DMSO at room temperature wasadded 0.005 gm of dimethylamino pyridine. A solution ofN,N'-dicyclohexyl carbodiimide (0.129 g) in 10 ml of DMSO was added tothe reaction mixture. After stirring for 4 hrs. at room temperature themixture was poured into water and extracted with chloroform. Thechloroform solution was washed with sodium bicarbonate, dried (MgSO₄)and evaporated. The product was chromatographed on silica andrecrystallized from toluene-petroleum ether to yield 0.123 g of yellowneedles which melted at 100° C.

What is claimed is:
 1. An article comprising:a substrate; and at leastone layer on said substrate of at least one substantially polymerizeddiacetylene, said diacetylene being crystallizable into a crystal havinga non-centrosymmetric unit cell, said article exhibiting sensiblenon-linear optical, piezoelectric or pyroelectric effects.
 2. Thearticle of claim 1 wherein said diacetylene has at least one chiralcenter.
 3. The article of claims 1, or 2 wherein said layer is bonded tosaid substrate covalently.
 4. The article of claim 3 wherein saidbonding comprises silicon-oxygen bonds.
 5. The article of claim 1further comprising a superstrate on said layer.
 6. The article of claim5 wherein both said substrate and said superstrate are bonded to saidlayer covalently.
 7. The article of claim 6 wherein said bondingcomprises silicon-oxygen bonds.